Four words of advice for African-Americans in the wake of George Zimmerman's acquittal:

Wake the hell up.

The Sunday after Zimmerman went free was a day of protest for many of us. From Biscayne Boulevard in Miami to Leimert Park in Los Angeles, to the Daley Center in Chicago to Times Square in New York City, African-Americans - and others who believe in racial justice - carried out angry, but mostly peaceful demonstrations.

Good. This is as it should have been.

But if that's the end, if you just get it out of your system, then move ahead with business as usual, then all you did Sunday was waste your time. You might as well have stayed home.

We are living in a perilous era for African-American freedom. The parallels to other eras have become too stark to ignore.

Every period of African-American advance has always been met by a crushing period of push-back, the crafting of laws and the use of violence with the intent of eroding the new freedoms. Look it up:

The 13th Amendment ended slavery. So the white South created a convict leasing system that was actually harsher.

The 14th Amendment guaranteed citizenship. So the white South rendered that citizenship meaningless with the imposition of Jim Crow laws.

The 15th Amendment gave us the right to vote; it was taken away by the so-called "grandfather clause." The Supreme Court struck that down, so the white South relied on literacy tests and poll taxes to snatch our ballots all over again.

Our history is a litany: two steps forward, one step back.

The Civil Rights Movement was the greatest step forward since emancipation. So we ought not be surprised to see voting rights eroded again, the Civil Rights Act attacked, the so-called "War on Drugs" used for the mass incarceration of black men. Or to see the killing of an unarmed child deliver a message as old as the Constitution itself: Black life is worth less.

We are in another period of push-back. And worse, we don't even seem to know.

It feels as if we have taken the great advances of the last half century - the protective laws, the rise of the black middle class, the winning of the ballot, the flowering of options once considered unthinkable - for granted. It feels as if we have come to regard progress as somehow inevitable, preordained, carved in stone and irrevocable as a birthright.

So yes, we need to wake the hell up.

While we were celebrating, others were calculating.

While we were writing nasty rap lyrics, they were writing senators.

While we were organizing Obama victory parties, they were organizing tea parties.

Page 2 of 2 - While we were buying DVDs, they were buying candidates.

While we were sending texts, they were building propaganda machinery.

While we were resting on the past, they were seizing the future.

Granted, the preceding casts a wide net. Yes, there are many of us, African-Americans and others, who don't need the admonition, who are already awake, who have always been awake. More power to them.

But there are also many of us still sleeping. So let Trayvon Martin's death and the acquittal of his killer be a wake-up call. Let it be a spur to stop reacting and start pro-acting. Let it be a goad to become better informed. Let it be a reminder to organize. Let it be a reason to send a check to the NAACP. Let it be an incentive to join the social justice ministry at church. Let it be cause to write your congressperson. Let it be an impetus to teach and nurture your kids.

Most of all, let it be an alarm clock, ringing in the darkness of a new morning, calling conscience to account. Do not waste this moment. The time for sleeping is done.

Leonard Pitts is a columnist with the Miami Herald. His email address is lpitts@herald.com.